Typically, vehicles use a timing belt or a timing chain to operate one or more camshafts and/or other accessories (e.g., oil and/or water pumps, balance shafts, etc.). Timing belts are preferred over timing chains for many reasons. For example, timing belts cost less and emit less noise than conventional timing chains when used in automobiles and other vehicles. Moreover, timing belts do not require lubrication and initially cost less than a timing chain. However, timing belts have a limited life span and typically require replacement in as little as 25,000 miles (as opposed to timing chains which can last for the life of the vehicle).
Because of high replacement cost, timing belts are usually neglected until they fail. However, timing-belt failure can lead to engine failure-especially in interference-type engines.
In addition to the fact that timing belts require more frequent replacement, this replacement can be tedious (and require many hours of work). For example, engine mounts, various pulleys and/or accessories such as power steering pumps, air conditioning compressors, alternators, etc. and/or their associated belts, pulleys, wiring, etc. must be removed to gain access to one or more timing belt covers which must be removed to gain access to the timing belt cavity. Thereafter, one or more tensioners, idler pulleys, water pumps, etc. must be adjusted and/or removed so that the timing belt can be removed and replaced. This process can take several hours and can be further complicated when an engine is of a V- or H-type configuration and/or includes a double overhead camshaft (DOHC) arrangement (as opposed to single overhead camshaft (SOHC) arrangement). Accordingly, timing-belt replacement costs can range from several hundred to a thousand dollars or more, of which only a few dollars is attributable to the cost of parts. Thus, consumers are inconvenienced and mechanics, as opposed to manufacturers, reap most of the profits from timing-belt replacement procedures.
A front view diagram illustrating a conventional timing belt arrangement in a DOHC (double overhead cam) inline engine configuration is shown in FIG. 1. For the sake of clarity, components such as a timing-belt cover, alternator, air conditioning (A/C) compressor, hydraulic pumps and their associated drive belts and/or associated pulleys and/or sprockets are not shown. A timing belt 10 is driven by a crankshaft sprocket (whose teeth are not shown for the sake of clarity) 12 and drives one or more camshaft sprockets (whose teeth are also not shown for the sake of clarity) 14 and 16 and may also drive one or more accessories (e.g., oil pump, balance shaft, etc.) 20. A tensioner pulley 18 provides tension to the timing belt 10. A front engine cover (aka an engine front cover) 26 which, for the sake of this discussion, can include all or part the engine's cylinder block, cylinder head, oil pan, front engine case, cylinder-head cover, water pump, oil pump, other elements, and/or combinations thereof, forms at least a part of a cavity for protecting the timing belt 10 (and associated components such as the pulleys, tensioners, balance belts, etc.) from being contaminated by the elements. The other part of the cavity may be formed, for example, by one or more timing-belt covers, etc. which, for the sake of clarity, are not shown. As shown, in a typical front-wheel-drive transverse-engine layout, a side motor mount 24 may be attached to the front engine cover 26 (and/or engine block and/or cylinder head). However, for the sake of clarity, throughout this application, a front engine cover will be referenced. A fluid passage 28 provides a means for transferring fluid to/from the engine. For example, as shown, the fluid passage 28 is a coolant passage for transferring coolant to/from a water pump (not shown) which is mounted adjacent to the fluid passage 28. As shown in the present application, it will be assumed that the crankshaft sprocket 12 rotates in a clockwise direction. However, other directions are also envisioned.
Typically, after the timing-belt (or belts) is installed, the one or more timing belt covers are used to protect the timing belt from the elements. Then, other components such as pulleys (e.g., a crankshaft pulley, harmonic balancer, etc.) are attached to an exposed end of the crankshaft (not shown). The crankshaft pulley is used to drive accessories such as the water, air and/or power-steering/hydraulic pumps, alternator, A/C compressor, etc. using one or more accessory drive belts.
Moreover, as typical timing-belt installation is complicated, timing belts are often incorrectly installed. Accordingly, it is not uncommon for components (such as cams, balance shafts, etc.) to be misaligned (i.e., mistimed) which can adversely affect fuel economy, timing, engine life, balance (e.g., resulting in vibration), and can lead to unexpected engine failure—which can occur at critical times. Moreover, improper tensioning, can allow a timing belt to skip, which can also result in unexpected failure (e.g., of the belt and the engine) and lead to a dangerous situation. For example, when a driver accelerates to cross a busy three-lane boulevard, if a timing belt skips cogs when the driver begins to accelerate, the engine can stall and leave the vehicle unexpectedly in the path of oncoming traffic.
Furthermore, because of high timing-belt replacement costs, used car values are affected by mileage and/or age (e.g., 5 years or 60,000 miles), which corresponds with timing belt replacement intervals. Moreover, because of these high costs, owners may avoid changing the timing belts (and related components) at recommended intervals, which can lead to unexpected engine failure. Further, typical variable valve timing systems adjust a rotational angle of a camshaft relative to a corresponding cam sprocket which is attached to the camshaft. This system typically requires a large number of parts which increases cost and the likelihood of failure. Moreover, typical variable valve timing systems require high-oil pressure (e.g., 1700 psi) lines for proper operation.
Accordingly, there is a need for an apparatus and a method for easily replacing timing belts in vehicles that avoid the problems and disadvantages of the prior art.